[Neidermeyer]

I wonder if this might be the cause.
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absolutely not ,, 8 bit is FINE , 16 bit is fine , 64 bit is fine ,,, you can count to infinity with any of them ... this is (if the story is correct) an application issue , not a problem with the computer the program runs on.

[who_would_fardels_bear]

In the "good old days" it was important to save space. In many cases software was written to save space, i.e. if a number wasn't expected to go above 32,768 then force it into 16 bits.

I'm well aware that you can count to infinity with even a single bit, but if the software was written assuming the need for just 16-bits for a particular intermediate result, and that result overflowed the 16-bits then errors will occur.

That typical air traffic flies around 30,000 feet and the U2 was at 60,000 just seemed to be an interesting coincidence to me with regard to binary numbers.